Technical Field
The present invention relates to ink, a method of manufacturing ink, and an ink cartridge.
Description of the Related Art
Inkjet recording methods have advantages such that the process is simple and full colorization is easy in comparison with other recording methods. Therefore, high resolution images can be obtained by a device having a simple configuration. For this reason, inkjet recording is widely diffusing from home use to office use, commercial printing, and industrial printing. However, aqueous ink using a water-soluble dye as the coloring material used in inkjet recording methods is inferior with regard to water resistance and light resistance. Therefore, pigment ink using a water insoluble pigment is under development.
For inkjet ink printing for office use, recording media, typically plain paper, are used and high image density is demanded. In general, when images are printed on plain paper using pigment ink, the pigment ink does not stay on the surface of the paper but permeates into the paper, so that the density of the pigment on the surface decreases and consequently the image density lowers. Image density increases if concentration of pigments in the ink is increased. However, the ink becomes viscous, thereby degrading the discharging stability of the ink.
Moreover, water contained in the pigment ink swells the surface of plain paper immediately after the ink droplets land on the paper. As a result, the extension percentage differs between the top surface and the bottom surface of the paper, which causes the paper to curl. This phenomenon does not cause a problem during low performance. However, as the printing speed increases, recording media are transferred (conveyed) before curling is canceled after printing, which naturally leads to occurrence of paper jam. To prevent this paper jam, it is suitable to add a permeating agent to a pigment ink to promote water to permeate into paper. However, ink becomes hydrophobic by the agent, which makes it difficult to secure storage stability of the ink. Also, the pigment ink more easily permeates into a recording medium, thereby furthermore decreasing image density.